The invention relates to a supervising and alarm method whose detection means are progressive in order to analyze the intensity of the breaking in and whose dissuasion and alarm means are progressive in intensity, in quality and in duration as a function of the detection.
Alarm systems constructed up to the present time are designed in accordance with roughly analogous functional diagrams.
One or more peripheral or volumetric detector loops are connected to the inputs of an alarm center. The alarm center has functions to supervise the various detectors in ways suitable to the principle of operation of each thereof and to set off the alarm when a disturbance is detected by a detector.
The alarm is given by various sound or light means or retransmitted over a distance by radio or telephone line. The sound warning means which are most usually employed as an alarm means are chosen in such a manner as to release a considerable amount of acoustic power which must be heard as far away as possible by the neighbors.
In the most sophisticated centers, an access loop permits the connection in a specific manner of the detector or detectors supervising the door through which the user will enter the premises under supervision. This permits avoiding the use of a lock contact placed outside the protected zone for connecting the system to the supply or stopping the system.
The user may thus enter by way of the door equipped in this way, without setting off the alarm. A pre-alarm, embodied by a light indicator or a buzzer of low sound level, will remind him to stop the center before the end of the time delay initiated by the opening of the door. If the center has not been stopped within the prescribed period, the alarm will be given.
In any cases, when a detector records a disturbance, the alarm will be given with all the powerful means provided for this purpose, either immediately for the normal loops or after a delay for the timed access loop.
The most serious problems created by alarm systems result from this feature common to all the presently-known systems. Indeed, security requirements combined with technological progress, encourage the installers to employ progressively sensitive detectors and to try to detect the attempted intrusions as early as possible and preferably before the intruder has entered the premises.
Unfortunately, in both cases, there is the same negative result: the proliferation of an ever larger number of accidental actuations. The difference between an attempted intrusion and a disturbance of atmospheric, electromagnetic or thermal origin is sometimes very slight or even non-existent. For example, the action of a violent wind on a badly-fitted door will be identical to that of the introduction of a crow-bar between the door and the frame for a detector operating under the effect of inertia placed on the door frame of the opening.
The effect of accidental actuations on the neighbors and on the users themselves is disastrous. They have an adverse effect on the value attached to an electronic alarm and give it a bad reputation in the eyes of potential clients.
Research workers and manufacturers of alarm equipment take great trouble to design more and more complex detectors in order to avoid these problems.
The present invention is the result of reflection on the finalities of electronic alarm systems. This type of alarm system is not intended to permit the capture of the burglars or thieves but to dissuade the latter from committing their crimes.